Device for developing a latent electrostatic image



Feb. 21, 1961 w. LIMBERGER 2,972,331

DEVICE FOR DEVELOPING A LATENT ELECTROSTATIC IMAGE Filed June 27, 1957Fig. 1

//v vz/vroe WA LTER LIMB ER ER X/Qm AGENT United States Patent a DEVICEFOR DEVELOPING A LATENT ELECTROSTATIC IMAGE Walter Liurberger, Hamburg,Germany, assignor to Lumoprint Zindler K.G., Hamburg, Germany, a companyof Germany Filed June 27, 1957, Ser. No. 68,523

Claims priority, application Germany June 29, 1956 Claims. (Cl. 118-637}The invention relates to a device for developing a latent electrostaticimage on a previously exposed xerog'raphic layer by the application ofpigment particles to a sheet carrying such layer and by fusion ofadhering pigment particles to the sheet.

The pigment particles are conventionally used in the development ofelectrostatic images carried by very small glass or quartz spheres oriron filings. The spheres or filings form with the pigment particles theso-called toner which,-because of the small size of its carrierelements, is pulverulent.

Known processes for the application of toner to xerographic sheetmaterial do not always achieve a uniform distribution of the particlesover the illuminated surface, even if a copious supply of toner is used.

The invention has for its object the provision of a simple apparatus forthe developing and fixing of a latent electrostatic image on axerographic layer forming part of a flexible carrier or sheet.

More particularly, the invention aims at providing a device of thischaracter in which the flexible carrier sheet is quickly and evenlyexposed to contact with a mass of toner particles and is immediatelythereafter subjected to a fusing operation, preferably withinterposition of means for removing excess toner particles from itssurface, so that the entire process is carried out rapidly and with aminimum of waste.

In accordance with this invention I provide a device of the general typereferred to in which a receptacle, containing a mass of granular toner,is internally provided with elongated, narrow upper and lower guideelements which are supported above the bottom of the receptacle andcurved with close vertical separation to a location below the tonerlevel, thereby forming a descending branch and an ascending branchadapted to guide the flexible carrier through the toner accumulation; aheating device, designed to fuse the adhering toner particles to thexerographic layer, is positioned adjacent the ascending branch of theguide elements. Advantageously, agitator means such as a mechanicalvibrator may be positioned just ahead of the heating device on an upwardextension of the path defined by the ascending branch of these elements.

The guide elements, which by virtue of their narrow configuration engageonly a small portion of the surface of the flexible carrier, arepreferably in the form of wires extending between an inlet slot and anoutlet slot for the carrier. These slots may be formed in a cover or lidwhich overlies the receptacle proper and also supports the wires.

Further advantages and features of the invention will appear from thefollowing description of an embodiment illustrated in the drawing inwhich:

Fig. 1 shows a side view of a device according to the invention; and

Fig. 2 shows a top-plan view of a receptacle forming part of the deviceof Fig. 1.

In the drawing, the container 2 and the heating device 2,972,33lPatented Feb. 21, 1961 ice 3 are arranged upon a base plate 1. Anagitator 4 is located beneath the heating device.

The container 2 is a substantially closed housing whose upper part canbe constructed, for example, as a cover 5. This housing or its cover 5is provided on opposite sides with two slots 6, 7 which serve as inletand outlet slots for the sheet carrying the xerographic layer. Asheet-guiding device, extending between the slots, is formed by wires 8,9. The wires preferably run parallel to the direction of advance of thesheet. it is also possible to arrange the wires at an inclination to thedirection of sheet movement. The Wires 8, 9 are arranged in severalpairs spaced over the width of the slots 6, 7, although the inner wirepairs shown in Fig. 2 could also be omitted to minimize interferencewith the passage of the toner through the sheet-guiding device.

The slots 6, 7 are so arranged in the container 2 that they lie abovethe toner 16 located in the container. The guides 8, 9 running betweenthe slots 6, 7 are so curved that they pass down into the toner 1h. Theextent of the curvature can be varied as desired. in the embodimentshown, the guides 8, 9 have a substantially straight section at alocation adjacent the inlet slot 6, thereafter curving sharply upwardsin front of the outlet slot 7. this construction, the sheet on leavingthe container 2, is pressed by the weight of the toner onto the lowerguide 9.

The sheet can be fed through the container by hand, by being pushed intothe slot 6 and thence passing between guides 8, 9 onto the guide path 12leading to the fusing device 3. The curvature of the guides 8, 9 and theloading of the sheet by the toner insures a correct positioning of thesheet for movement through the guiding path 12, yet such movement canalso be expedited by Withdrawing the sheet from the heating device tothe right over the rounded edge 11. it will be understood that the sheetcan also be provided with projections to facilitate its displacementthrough the apparatus and that automatic feeding means known per se,such as pairs of electrically driven rollers, might be used for itsdisplacement.

The guide path 12 for the fusing device runs straight from the terminalportion of the guides 8, 9. The guide path is inclined upwardly in theembodiment shown. Above the guide path is located an arrangement ofinfrared lamps 13, 14 which are covered by parabolic reectors 15, 16, sothat the developed heat is directed towards the guide path 12. There isalso the possibility of providing heating devices 17, 17', 17", 17'beneath the guide path, instead of or in addition to the infra-red lamps13, 14, by which the carrier sheet is heated at its reverse side, thatis on the side not provided with the xerographic layer, in order to fusein the pigment particles.

The illustrated curvature of the guides 3, 9 extending through thecontainer 2 and the direction of the guide path 12 have the advantagethat adherent excess particles fall back into the container 2 as thesheet passes out from the toner it To expedite this process, theagitation 4 is provided whose vibratory element 18 contacts the reverseside of the sheet between the guides 8, 9 and the guide path 12. Thiselement consists of a resilient transverse bar which engages the sheetover its whole width. Bar is secured to the free arm of a crank leverwhose other arm is pivotally mounted at 2.0 in a horizontal guide slot.The arm 19 is oscillated by a drive motor 21 by way of a cam 23 securedto the motor shaft 22.

In a further development of the illustrated device according to theinvention, the drive 21 for the crank lever 19 can agitate the container2 which in this case is pivotally mounted or suspended. The oscillationof the container 2 with a small amplitude leads to continual looseningand shaking of the toner and hence at the same time facilitates thepassage of the carrier sheet through the guides 8, 9. The amplitude ofthe oscillation is preferably parallel to the direction of advance ofthe sheet, though it could also be perpendicular to the base of thecontainer.

The device according to the invention operates with extreme simplicityso that it requires very little supervision. At the same time, anextremely compact construction is provided wherein, particularly throughthe positioning of the guide path 12 beneath the heating device, spaceis provided for the vibrator 4. This gives the possibility ofaccommodating the entire developing apparatus in a very small space. Itis also possible to mount this assembly in the frame of anotherapparatus, in which at the same time the illumination and/or charging ofthe xerographic layer is carried out.

What I claim is:

1. A device for developing, by contact with a granular toner, a latentelectrostatic image on a flexible carrier having a xerographic layer,comprising a receptacle adapted to be filled to a predetermined levelwith said toner, elongated, narrow upper and lower guide elementssupported on said receptacle above the bottom thereof, said guideelements fixedly extending with close vertical separation across the topof said receptacle and curving down therewithin to a location below saidlevel, thereby forming a descending branch and an ascending branchadapted to guide said carrier through an accumulation of said tonerwithin said receptacle, and heating means adjacent said ascending branchfor fusing adhering toner particles to said carrier.

2. A device according to claim 1 wherein said ascending branch extendson a slope in the region of said heating means.

3. A device according to claim 1, further comprising agitating meanspositioned at said ascending branch below said heating means forremoving loosely entrained particles from said carrier upon emergence ofthe latter from said receptacle.

4. A device according to claim 3 wherein said agitating means comprisesa transverse bar extending across the path of said carrier, rotatablecam means, link means operatively connecting said bar with said cammeans, and drive means for rotating said cam means.

5. A device fordeveloping, by contact with a granu lar toner, a latentelectrostatic image on a'flexible carrier having a xerographic layer,comprising a receptacle adaptedto be filled to a predetermined levelwith said toner, a lid overlying said receptacle, said lid beingprovided on opposite sides with a pair of parallel, horizontal slotsrespectively constituting an inlet slot and an outlet slot for saidcarrier, narrow, elongated upper andlower stationary guide elementsclosely vertically separated from'each other at their extremities bysaid slots and *maintaining their vertical separation throughout theirlength, said guide elements depending from said lid and extendingbetween said slots to a location below said level, thereby forming adescending branch and an 'ascending branch adapted to guide said carrierthrough an accumulation of said toner within said receptacle, and

heating means adjacent said ascending branch for fusing adhering tonerparticles to said carrier.

6. A device according to claim 5, further comprising an upwardly slopingextension of said guide elements above said outlet slot, said heatingmeans being 10- oated adjacent said extension.

7. A device according to claim 6, further comprising agitator meanspositioned at said extension below said heating means for removingloosely entrained particles from said carrier upon emergence of thelatter from said outlet slot.

8. A device according to claim 6 wherein said extension terminates in agently'rounded shoulder at its upper end.

9. A device for developing, by contact with a granular toner, a latentelectrostatic image on a flexible carrier having a xerographic layer,comprising a receptacle 1 adapted to be filled to a predetermined levelwith said toner, a plurality of pairs of downwardly arched,substantially parallel wires supported on said receptacle above thebottom thereof, said wires fixedly extending with close verticalseparation across the top of said receptacle and curving downtherewithin to a location below said level, thereby forming a descendingbranch and an ascending branch adapted to guide said carrier through anaccumulation of said toner within said receptacle, and heating meansadjacent said ascending branch for fusing adhering toner particles tosaid carrier.

10. A device for developing, by contact with a granular toner, a latentelectrostatic image on a flexible carrier having a xerographic layer,comprising a receptacle adapted to be filled to a predetermined levelwith said toner, a lid overlying said receptacle, said lid beingprovided on opposite sides with a pair of parallel, horizontal slotsrespectively constituting an inlet slot and an outlet slot for saidcarrier, a plurality of pairs of downwardly arched, substantiallyparallel wires separated from each other at their extremities by saidslots and maintaining their vertical separation throughout their length,said Wires depending from said lid and extending between said slots to alocation below said level, thereby forming a descending branch and anascending branch adapted to guide said carrier through an accumulationof said toner within said receptacle, and heating means adjacent saidascending branch for fusing adhering toner particles to said carrier.

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